Humoral immunity and cell-mediated immunity are the two major branches of the mammalian immune response. Humoral immunity involves the generation of antibodies to foreign antigens. Antibodies are produced by B-lymphocytes. Cell-mediated immunity involves the activation of T-lymphocytes which either act upon infected cells bearing foreign antigens or stimulate other cells to act upon infected cells. Both branches of the mammalian immune system are important in fighting disease. Humoral immunity is the major line of defense against bacterial pathogens. In the case of viral disease, the induction of cytotoxic T lymphocytes (CTLs) appears to be crucial for protective immunity. An effective vaccine stimulates both branches of the immune system to protect against disease.
Vaccines present foreign antigens from disease causing agents to a host so that the host can mount a protective immune response. Often vaccine antigens are killed or attenuated forms of the microbes which cause the disease. The presence of non-essential components and antigens in these killed or attenuated vaccines has encouraged considerable efforts to refine vaccine components including developing well-defined synthetic antigens using chemical and recombinant techniques. The refinement and simplification of microbial vaccines, however, has led to a concomitant loss in potency. Low-molecular weight synthetic antigens, though devoid of potentially harmful contaminants, are themselves not very immunogenic. These observations have led investigators to add adjuvants to vaccine compositions to potentiate the activity of the refined vaccine components.
Presently, the only adjuvant licensed for human use in the United States is alum, a group of aluminum salts (e.g., aluminum hydroxide, aluminum phosphate) in which vaccine antigens are formulated. Particulate carriers like alum serve to promote the uptake, processing and presentation of soluble antigens by macrophage. Alum, however, is not without side-effects and enhances humoral (antibody) immunity only.
An effective adjuvant potentiates both a humoral and cellular immune response in vaccinated animals. Further, an adjuvant must enhance a host""s natural immune response and not aggravate the host system. A well-defined synthetic adjuvant free from extraneous matter which is stable and easy to manufacture would provide these qualities. Compounds that have been prepared and tested for adjuvanticity (Shimizu et al. 1985, Bulusu et al. 1992, Ikeda et al. 1993, Shimizu et al. 1994, Shimizu et al. 1995, Miyajima et al. 1996), however, often display toxic properties, are unstable and/or have unsubstantial immunostimulatory effects.
The discovery and development of effective adjuvants is essential for improving the efficacy and safety of existing vaccines. Adjuvants impart synthetic peptide and carbohydrate antigens with sufficient immunogenicity to insure the success of the synthetic vaccine approach. There remains a need for new compounds having potent immunomodulating effects.
The compounds of the subject invention are aminoalkyl glucosamine phosphate compounds (AGPs) which are adjuvants and immunoeffectors. An aminoalkyl (aglycon) group is glycosidically linked to a 2-deoxy-2-amino-xcex1-D-glucopyranose (glucosamine) to form the basic structure of the claimed molecules. The compounds are phosphorylated at the 4 or 6 carbon on the glucosamine ring. Further, the compounds possess three 3-alkanoyloxyalkanoyl residues.
The compounds of the subject invention are immunoeffector molecules augmenting antibody production in immunized animals, stimulating cytokine production and activating macrophage. In accordance with the subject invention, methods for using these compounds as adjuvants and immunoeffectors are disclosed.
The compounds of the subject invention are adjuvant and immunoeffector molecules which are aminoalkyl glucosamine phosphates (AGPs). The compounds comprise a 2-deoxy-2-amino-xcex1-D-glucopyranose (glucosamine) in glycosidic linkage with an aminoalkyl (aglycon) group. Compounds are phosphorylated at the 4 or 6 carbon on the glucosamine ring and have three alkanoyloxyalkanoyl residues. The compounds of the subject invention are described generally by Formula I, 
wherein X represents an oxygen or sulfur atom, Y represents an oxygen atom or NH group, xe2x80x9cnxe2x80x9d, xe2x80x9cmxe2x80x9d, xe2x80x9cpxe2x80x9d and xe2x80x9cqxe2x80x9d are integers from 0 to 6, R1, R2, and R3 represent normal fatty acyl residues having 7 to 16 carbon atoms, R4 and R5 are hydrogen or methyl, R6 and R7 are hydrogen, hydroxy, alkoxy, phosphono, phosphonooxy, sulfo, sulfooxy, amino, mercapto, cyano, nitro, formyl or carboxy and esters and amides thereof, R8 and R9 are phosphono or hydrogen. The configuration of the 3xe2x80x2 stereogenic centers to which the normal fatty acyl residues are attached is R or S, but preferably R. The stereochemistry of the carbon atoms to which R4 or R5 are attached can be R or S. All stereoisomers, both enantiomers and diastereomers, and mixtures thereof, are considered to fall within the scope of the subject invention.
The heteroatom X of the compounds of the subject invention can be oxygen or sulfur. In a preferred embodiment, X is oxygen. Although the stability of the molecules could be effected by a substitution at X, the immunomodulating activity of molecules with these substitutions is not expected to change.
The number of carbon atoms between heteroatom X and the aglycon nitrogen atom is determined by variables xe2x80x9cnxe2x80x9d and xe2x80x9cmexe2x80x9d. Variables xe2x80x9cnxe2x80x9d and xe2x80x9cmxe2x80x9d can be integers from 0 to 6. In a preferred embodiment, the total number of carbon atoms between heteroatom X and the aglycon nitrogen atom is from about 2 to about 6 and most preferably from about 2 to about 4.
The compounds of the subject invention are aminoalkyl glucosamine compounds which are phosphorylated. Compounds can be phosphorylated at position 4 or 6 (R8 or R9) on the glucosamine ring and are most effective if phosphorylated on at least one of these positions. In a preferred embodiment, R8 is phosphono and R9 is hydrogen.
The compounds of the subject invention are hexaacylated, that is they contain a total of six fatty acid residues. The aminoalkyl glucosamine moiety is acylated at the 2-amino and 3-hydroxyl groups of the glucosamine unit and at the amino group of the aglycon unit with 3-hydroxyalkanoyl residues. In Formula I, these three positions are acylated with 3-hydroxytetradecanoyl moieties. The 3-hydroxytetradecanoyl residues are, in turn, substituted with normal fatty acids (R1-R3), providing three 3-n-alkanoyloxytetradecanoyl residues or six fatty acid groups in total.
The chain length of normal fatty acids R1-R3 can be from about 7 to about 16 carbons. Preferably, R1-R3 are from about 9 to about 14 carbons. The chain lengths of these normal fatty acids can be the same or different. Although, only normal fatty acids are described, it is expected that unsaturated fatty acids (i.e. fatty acid moieties having double or triple bonds) substituted at R1-R3 on the compounds of the subject invention would produce biologically active molecules. Further, slight modifications in the chain length of the 3-hydroxyalkanoyl residues are not expected to dramatically effect biological activity.
The compounds of the subject invention are adjuvants and immunoeffectors which enhance the generation of antibody in immunized animals, stimulate the production of cytokines and stimulate a cell-mediated immune response including a cytotoxic T-lymphocyte response. In methods for effecting the immune response of an individual, the compounds of the subject invention can be formulated with a pharmaceutically acceptable carrier for injection or ingestion. As used herein, xe2x80x9cpharmaceutically acceptable carrierxe2x80x9d means a medium which does not interfere with the immunomodulatory activity of the active ingredient and is not toxic to the patient to whom it is administered. Pharmaceutically acceptable carriers include oil-in-water or water-in-oil emulsions, aqueous compositions, liposomes, microbeads and microsomes.
Formulations of the compounds of the subject invention that can be administered parenterally, i.e. intraperitoneally, subcutaneously or intramuscularly include the following preferred carriers. Examples of preferred carriers for subcutaneous use include a phosphate buffered saline (PBS) solution and 0.01-0.1% triethanolamine in USP Water for Injection. Suitable carriers for intramuscular injection include 10% USP ethanol, 40% propylene glycol and the balance an acceptable isotonic solution such as 5% dextrose.
Examples of preferred carriers for intravenous use include 10% USP ethanol, 40% USP propylene glycol and the balance USP Water for Injection. Another acceptable carrier includes 10% USP ethanol and USP Water for Injection; yet another acceptable carrier is 0.01-0.1% triethanolamine in USP Water for Injection. Pharmaceutically acceptable parenteral solvents are such as to provide a solution or dispersion may be filtered through a 5 micron filter without removing the active ingredient.
Examples of carriers for administration via mucosal surfaces depend upon the particular route. When administered orally, pharmaceutical grades of mannitol, starch, lactose, magnesium stearate, sodium saccharide, cellulose, magnesium carbonate and the like, with mannitol being preferred. When administered intranasally, polyethylene glycol or glycols, sucrose, and/or methylcellulose, and preservatives such as benzalkonium chloride, EDTA, may be used, with polyethylene glycols being preferred, and when administered by inhalation, suitable carriers are polyethylene glycol or glycols, methylcellulose, dispensing agents, and preservatives, with polyethylene glycols being preferred.
The compounds of the subject invention are administered to an individual in xe2x80x9can effective amountxe2x80x9d to effect or enhance the individual""s immune response. As used herein, xe2x80x9can effective amountxe2x80x9d is that amount which shows a response over and above the vehicle or negative controls. The precise dosage of the compounds of the subject invention to be administered to a patient will depend upon the particular AGP used, the route of administration, the pharmaceutical composition, and the patient. For example, when administered subcutaneously to enhance an antibody response, the amount of AGP used is from 1 to about 250 micrograms, preferably from about 25 to about 50 micrograms based upon administration to a typical 70 kg adult patient.
In vaccine compositions, the AGPs of the subject invention are administered to a warm-blooded animal, including humans, with an antigen. The amount of antigen administered to elicit a desired response can be readily determined by one skilled in the art and will vary with the type of antigen administered, route of administration and immunization schedule. For example, 0.2 xcexcg of tetanus toxoid administered with the claimed compounds subcutaneously to a mouse in two immunization 21 days apart elicited a humoral immune response to that antigen.
The compounds of the subject invention are synthesized by coupling an N-acyloxyacylated or N-protected aminoalkanol or aminoalkanethiol (aglycon unit) with a suitably protected and/or 3-O-acyloxyacylated glucosamine unit. In one preferred method for preparing the compounds of the subject invention (Scheme 1), an N-(2,2,2-trichloroethoxycarbonyl (Troc))-protected glycosyl halide 1 (Z=F, Cl, Br) is coupled with an N-[(R)-3-n-alkanoyloxytetradecanoyl]aminoalkanol or thiol 2 (possessing R6 and R7 in suitably protected form) via a Koenigs-Knorr type reaction in the presence of mercury or silver salts to give glycoside intermediate 3. Preferably, the glucosamine unit 1 possesses an anomeric chloride atom (Z=Cl), and the coupling catalyst is silver trifluoromethanesulfonate. Intermediate 3 can also be prepared by coupling the aglycon unit 2 with an N-Troc-protected glycosyl acetate (Z=OAc) or related activated derivative in the presence of a Lewis acid such as boron trifluoride etherate. By xe2x80x9cactivatedxe2x80x9d is meant having an appropriate displaceable leaving group xe2x80x9cZxe2x80x9d attached to the anomeric center of the glucosamine unit. Glucosamine unit 1 bears an (R)-3-n-alkanoyloxytetradecanoyl residue on the 3-position, and suitable protecting groups on the 6-hydroxyl and 4-phosphate moieties. Typical protecting groups for the phosphate group include, but are not limited to, phenyl, benzyl, and o-xylyl. The phosphate group is protected preferably with two phenyl groups. The 6-position can be temporarily protected by blocking groups commonly used in sugar chemistry such as silyl, benzyl, or benzyloxymethyl ethers or, alternatively, an alkyl carbonate. The 6-hydroxyl group is protected preferably as a 1,1-dimethyl-2,2,2-trichloroethyl carbonate (TCBOC).
The trichloroethyl-based protecting group(s) in the Koenigs-Knorr coupled product 3 are removed with zinc and the glucosamine nitrogen is selectively acylated with a (R)-3-n-alkanoyloxytetradecanoic acid 4 in the presence of a suitable coupling reagent to give the hexaacylated derivative 5. The remaining protecting groups in 5 are then cleaved by catalytic hydrogenation in the presence of a palladium or platinum catalyst or by other appropriate means to give compounds of Formula (I).
A suitable starting material for the synthesis of glycosyl donor 1 is 2-(trimethylsilyl)ethyl 2-amino-2-deoxy-4,6-O-isopropylidene-xcex2-D-glucopyranoside which can be prepared from commercially available D-glucosamine hydrochloride using published procedures. The conversion of the 2-(trimethylsilyl)ethyl glycoside starting material to glycosyl donor 1 can be achieved by methods known in the art or modifications thereof which are described herein. The aglycon unit 2 can be prepared by N-acyloxyacylation of commercially available starting materials with an appropriate (R)-3-n-alkanoyloxytetradecanoic acid 4, or N-acyloxyacylation of starting materials that can be obtained by known methods in the chemical literature. Alternatively, the N-acyloxyacyl residue in 2 can be substituted with an appropriate amine protecting group which is removed subsequent to the coupling reaction such as is described in the second preferred embodiment below.
In a second preferred method for preparing the compounds of the subject invention (Scheme 2), introduction of the (R)-3-n-alkanoyloxytetradecanoyl and phosphatic groups into the glucosamine and aglycon units is performed subsequent to the glycosylation (coupling) reaction using N- and O-protecting groups suitable for the chemical differentiation of the amino and hydroxyl groups present. Preferably, the N-Troc-protected glycosyl donor 6 is coupled with an N-allyloxycarbonyl (AOC)-protected aminoalkanol or thiol 7 in the presence of an appropriate catalyst to give the aminoalkyl xcex2-glycoside 8. Most preferably, the glycosyl donor 6 possesses an anomeric acetoxy group (Z=OAc), and the coupling catalyst is boron trifluoride etherate. Other N-protecting groups for the aglycon amino group include, but are not limited to, commonly employed carbamates obvious to one skilled in the art such as t-butyl (t-BOC), benzyl (Cbz), 2,2,2-trichloroethyl (Troc), and 9-fluorenylmethyl(Fmoc). Base-induced cleavage of the acetate groups in coupling product 8 and 4,6-acetonide formation under standard conditions known in the art gives intermediate 9. 3-O-Acylation of 9 with (R)-3-n-alkanoyloxytetradecanoic acid 4, followed by palladium(0)-mediated removal of the aglycon N-AOC group and N-acylation with (R)-3-n-alkanoyloxytetradecanoic acid 4 provides intermediate 10. Acetonide hydrolysis and functionalization of the 4- and 6-positions as described herein for the preparation of glycosyl donor 1 gives intermediate 3 (Y=O) which is then processed as in Scheme 1 to afford compounds of general Formula (I).